Many nutritional supplements are available on store shelves with little to no indication as to their safety when taken with one or more other ones. Two supplements that fall into this category are 5-hydroxytryptophan and gamma-aminobutyric acid, more commonly known as 5-HTP and GABA. Combining these supplements in small doses may be safe, but sufficient research does not exist regarding their effects in combination on the human body.
GABA is a naturally occurring neurotransmitter that helps to modulate the firing of neurons in your central nervous system when present in your brain. Because of this effect, manufacturers often claim that GABA is useful for relaxation and as a sleep aid. The supplement 5-HTP is a precursor to the mood-calming chemical serotonin, and some studies have shown it to be effective in treating depression and insomnia. Though 5-HTP has been demonstrated to be mildly effective, GABA has not for most uses, because it has difficulty crossing the blood-brain barrier. Therefore, GABA is unlikely to provide any additional relaxation effects when used in combination with 5-HTP.
According to the NYU Langone Medical Center, there are no known contraindications for GABA, meaning that it is potentially safe to take it with 5-HTP. However, the medical institution adds that there are no significant studies regarding GABA's interactions with other supplements, so there is no guarantee that you can safely use them in combination.
Little is known about the interaction of 5-HTP and GABA in supplement form, but it is likely that you have consumed both in limited doses from your diet. In a GABA safety proposal received by the U.S. Food and Drug Administration in 2008, the research team of Pharma Foods International states that GABA naturally occurs in small doses in fermented foods, melons, tomatoes and potatoes. 5-HTP does not occur naturally in food, but its precursor amino acid tryptophan occurs in turkey, milk and potatoes.
Best-selling supplement author Ray Sahelian, MD claims that you are unlikely to have a negative drug interaction when you combine 5-HTP and GABA in small amounts. He adds that you should always speak to a physician before combining the two supplements, because each person has a unique physiology that may present complications. Recommended dosages for GABA can range widely from 10 mg to 1000 mg depending on its prescribed use, and 5-HTP carries a recommended dosage of up to 150 mg per day.